Please reset router to factory settings to avoid problems with some previous configuration.
Connect your computer using LAN cable from the Ethernet port on your Laptop / PC to the PoE In port on the Ubiquiti AirGateway router.
Set static IP address in 192.168.1.x range
In the address bar of the web browser, enter 192.168.1.1 and login using admin as username and password as password.

From the System tab using Choose File button navigate to location on your computer hard drive from where you will update firmware.
Click Upload button and then click the Ok button to proceed with the firmware update.
Once the process is complete, the device will reboot.
This process will take a few minutes.
After that you will need to reconnect LAN cable or to Disable/Enable NIC card in order to get new valid IP address in 192.168.45.x range from router.

Configuring parameters

On Status page you will see a MAC address of your OpenWRT router which will be used in the SignUp process.
After selecting your HotSpot name, select as HotSpot model OpenWRT, and add your MAC address from Status tab.

From Setup page configure your OpenWRT router. Be sure that you set Autostart option. This option is not active by default.
Here you can set new Administrator password for access to the router setup and configuration.
Enable WiFi and set your SSID name.
On DNS select as Server to use GoogleDNS.
For Network select to use DHCP.
When you finish with the settings press Save button on bottom of the page.

If you need help with configuration, please go to starthotspot.com and contact our tech support. We'll be glad to help you.